C＃PLINQ .AsParallel（）在查询中的位置

Question

StackOverflow,

Within C# PLINQ I understand the position of ".AsParallel()" impacts how the query is run. For example, where ".AsParallel()" occurs in the middle of a query it will execute sequentially before the method and parallel after the method. ( PLINQ: Parallel Queries in .NET ).

My question is, with a more complex query (below), where ".AsParallel" occurs at the start of the query (as a prefix to .Select) will all following methods execute parallel also? (currently, ".AsParallel" occurs after the .Select).

  Collection =
   typeof (Detail).GetProperties(BindingFlags.Public | BindingFlags.Instance)
     .SelectMany(propertyInfo => recentPhases
      .Where(phase => phase.Finalised)
      .SelectMany(phase => phase.PhaseDetail
      .Select(keyValuePair => new
     {
      phase.Direction,
      phase.Momentum,
      keyValuePair.Key,
      keyValuePair.Value
     }))
     .Select(arg => new
     {
      Key = new BmkKey
      {
       Direction = (arg.Direction == Dir.Up ? Dir.Up : Dir.Down),
       Momentum = (arg.Momentum == Mom.Price ? Mom.Price : Mom.Time),
       BarNumber = arg.Key,
       DetailType = propertyInfo.Name
      },
      Value = (double) propertyInfo.GetValue(arg.Value, null)
     }))
    .AsParallel().GroupBy(grp => grp.Key)
    .ToDictionary(grp => grp.Key, grp => new Distribution(grp.Select(x => x.Value)));

Answer 1

Yes everything will be executed parallel after the AsParallel() method is called. From msdn:

public static ParallelQuery<TSource> AsParallel<TSource>(
this IEnumerable<TSource> source)

So the input is an IEnumerable<T> and the output a ParallelQuery<T> .

If we then look at the ParallelEnumerable class :

Provides a set of methods for querying objects that implement ParallelQuery{TSource}. This is the parallel equivalent of Enumerable.

So from then on, you won't be calling the methods defined for IEnumerable<T> but you will be calling their parallel counterparts defined for ParallelEnumerable .